Xtreme Power Systems

[kgfly]

No, it is because the FCC certification for the XPS Tx module is inherited from the XBeePro module inside. That certification is for use of the module with three specific antenna setups. Use with any other setup would require recertification and so XPS, as the manufacturer of the module, have to say that using a non-approved antenna configuration is indeed illegal.

Spektrum on the other hand have had their modules certified specifically with the antenna-on-a-string setup.

[DavidH]

Got a link to the certification information on the FCC site ?

David

[flymo]

Product design......really should have done some.

[Motions]

XPS arrived in the mail today. Check your boxes.

The new modules have new firmware so Be sure you get the updated manual. Programming is easier and you can select specific channels for user defined failsafe. Default is last position.

I set it up and did a range check and all worked well. The manual says "remove the external antenna" for range check and I assumed that is the new screw in antenna. Got about 150 ft. with no antenna and low power.

Made a VERY careful flight test and it went great. I did have to reduce my gyro gain by 5%. I had some wag with the XPS receiver and I can only assume that the speed increased from PPM 2.4GHz.

I have to say, like most of you, I don't like the new antenna. You can't lay your radio down and you have to remove the antenna if your using a carrying case. Other than that, I look forward to some more testing.

[cricket]

Arrived today 8 and 10 channel receivers. Maybe a test flight later today. New style antenna system.

[kgfly]

Got a link to the certification information on the FCC site ?

DavidNo but I believe the FCC ID is OUR-XBEEPRO so you could search for that on the FCC site.

[DavidH]

I did a search of the FCC site. Didn't find anything about a certification for XPS or XBeePro.
That is why I asked if you had a link, You seem to know about the FCC certifications

David

[kgfly]

I am not an expert in these things but I think this it the document you are looking for: https://gullfoss2.fcc.gov/prod/oet/forms/blobs/retrieve.cgi?attachment_id=598855&native_or_pdf=pdf

Looking at it more closely it is certified with the onboard chip antenna and 3 kinds of external antenna so long as a cable with the right loss is used. Perhaps I missed it but I cannot see where the on-board whip antenna is covered. :dontknow

[Pinecone]

May be a new addition that hasn't made it to the cert document online.

[fireup]

Sinse XPS uses XBeePro Modules made by MaxStream, are they the same modules? or are the firmware of the modules different?

[Pinecone]

According to Jim Drew, they are based on teh MaxStream, but are not the same production modules as you can buy. He won't go into specifics on what has been changed.

But the firmware for sure, and the antenna was another, although due to some fileds with high noise floors, they are changing the Tx antenna to a more conventional one.

[ClayK]

I'm curious, if the XBEE PRO modules have a LOS (Line of Sight) RF range of 1 mile (at 100mW)..... How can the XPS parts that use this module have 5 times the range and not be LOS?

Am I missing something???? :dontknow

[DavidH]

I wonder about the same thing. But then again it could be just marketing.

David

[kgfly]

I suspect the key factor is ground-to-ground vs ground-to-air. They gave test results for 5 mile range from ground level t o a 150ft tower achieving 90% packet throughput.

[DavidH]

They gave test results for 5 mile range from ground level t o a 150ft tower achieving 90% packet throughput.


What kind of test results? I personally don't call it a test unless they are using the product? Put it in a model and see how far from the transmitter it can be flown before LOS. I think LOS will happen long before the model gets 5 miles away.

I have never had a 150 ft tower fly, but I have flown in to one about that tall with a model. LOL

David

[Motions]

If you can fly it a mile away and still see it, I have a medical research project for you.

[kgfly]

Put it in a model and see how far from the transmitter it can be flown before LOS.We will see lots of this sort of data over the next month. Already many reports of "I specked it out without a problem" which probably means 1500-3000ft. With the DX6 and DX7 some very methodical folk did quite impressive testing. For example they took the Rx up in a real heli or light aircraft with a GPS tracker and tested the range from a Tx on the ground. I am hoping to see similarly informative tests done on XPS.

Of course whether it's 1 mile or 5 miles is surely a purely academic "truth in advertising" question isn't it? One mile is plenty for 99% of pilots and surely 99.99% of heli pilots I would guess.

[DavidH]

That is my point. LOL
Thou I have flown with a couple of pilots, it amazes me how far they can fly the model away from themselves and still see it. I would say they are going to close to a mile before they turn around.

Like I said, marketing .

David

[kgfly]

BTW - Another high profile jet crash flying Spektrum was just confirmed to be a brownout problem with an overloaded regulator (19 servos on a 7.5A reg). It is clear that the longer reboot/reacquisition times of the 2.4Ghz Rx are exposing weak power-supplies. XPS say theirs is much faster than Spektrum's so that could be a good thing. This whole issue of brief voltage dips below 3.7V has claimed quite a few models now from foamies to helis to large 3D gassers and jets. This information should force a lot of folk to reassess their BEC setups, certainly if they want to move to 2.4G solutions. AFAIK there are now at least 3 brands with integrated switched mode BECs: Jazz, Jeti and Hyperion. I am hoping we will see a transition to integrated switched mode BECs over the next six to twelve months as demand increases. Since the retail price of a standalone ubec is $10-$20 I don't see why ESCs with integrated ones need to cost more than $20 above those with linear regulators.

[ClayK]

RF is spherical in nature. Signal degradation happens at the extent of range or due to obstacles. How does ground to ground communication differ from ground to air communication? It's the same distance regardless. What should be noted is that ground to ground communication has more obstacles than ground to air, hence the question about LOS. Signal saturation and RF Engineering isn't a course you can take, it's a skill/vocation learned on the job, unless things have changed since I was managing cell platform construction and aggregate radiation studies on antenna platforms. :dontknow

There's marketing and then there's exaggeration of a products specifications. A simple Logic class defuncts the statements. I don't think I have to elaborate, just about everyone here has taken a Logic 100 level course in College or at least has some sort of deductive reasoning that wouldn't require such a course.

[kgfly]

Ground-to-ground and ground-to-air are different to some degree at least due to the affects of the Fresnel zone:

http://en.wikipedia.org/wiki/Fresnel_zone
http://www.maxstream.net/support/knowledgebase/article.php?kb=90

Even the ground itself, with no other obstacles, reduces range within the Fresnel zone. Then you add vegetation and other obstacles too and the affect is even greater.

At a 1mile separation between Tx and Rx the Fresnel zone has a radius (or diameter depending upon which reference you believe :( ) of approx 20ft and at 5 miles approx 50ft. For the purpose of discussion let's assume the worst case which is that these figures represent the radius, hence we have to get somewhere over 50ft to 100ft above the average ground level to get out of the Fresnel zone plus maybe a bit more if there are any significant obstacles along the way.

In order for a wireless link to work, the available system operating margin (TX power - RX Sensitivity + Antenna gains) must exceed the Freespace loss and all other losses in the system.
For the XPS:
Tx power = 20dBm
Rx sensitivity = -100dBm (at least for the stock XBeePro module)
Antenna gain = 2.1dBi x 2 (I think)
So we get 20 - (-100) + 4.2 = 124.2dBm which puts range between 1 mile and 10 miles so long as we are out of the Fresnel zone, say over 100ft.

Even if this estimate is out by 6dB (a factor of 4) it still estimates range well in excess of 1 mile ground-to-air so it seems to me there could be a basis for the claims.

[spork]

Ground-to-ground and ground-to-air are different to some degree at least due to the affects of the Fresnel zone:

No question about it. The difference can be tremendous depending on signal frequency and strength. I've seen it all too clearly in my work. You can also prove it easily with an antenna extended range check of your model, and I'll offer the best example I can think of...

We use handheld ham radios (2 meter) to communicate with each other and our drivers when we hang glide. It's critical that you give your driver your coordinates before you land, because once on the ground your range is crap. From mountain-top to mountain-top I've had crystal clear communication between 5 watt handhelds for literally 100's of miles. I've never had any range even remotely approaching that even on the flattest ground.

[ClayK]

While the Fresnel zone is applicable to frequency transmission and saturation, it still does not increase the range by a factor of 5 for air-to-air transmission over (what is perceived to be) ground-to-air transmission. I'm familiar with the theoretical aspects of the "Fresnel Zone", however, please note my areas of concern listed below.

1. Regardless of the type of transmission, the signal is strongest in a straight line from transmit to receipt. A simple A to B is covered even in the F Zone. The distance is still the same, if you want to use Wikipedia, note callouts B and D. D is the distance from one point to another, as is the B line. The B delta is the elliptical "sphere" that is radiated from the LOS transmission.

2. As noted, even on that "reference" page, RF is Line of Sight. XPS claims that LOS does not apply to their TX module and RX. How can this be possible when all RF is LOS? (please note that the exception is spherical "bounces" which are still straight line transmissions that bounce the signal off of atmospheric layers). One can apply a geometrical approach to transmission and receipt.

3. The transmission, using F Zone, is elliptical in nature. This means that the range is not increased from end to end, but merely broaden along it's axis. Application of this theory only solidifies my previous statement that the range cannot be increased based on air-to-air over ground-to-air.


Obstacles impede the signal in ground-to-ground transmission, but to make an unsubstantiated claim that is increased by a factor of 5 seems a little bit questionable in my opinion. In addition, making the claim that "your" application doesn't apply the basic rule of Line Of Sight, even though the base module (XBEE) specifies this, also seems questionable.

Don't get me wrong, I'm not attacking the product, I'm attacking what I believe to be inaccurate claims. The product may be an excellent product, but that doesn't justify exaggerating claims to the nTH degree to increase revenue. To make an analogy, this would be akin to Hyundai claiming all their cars were 7 second quarter-milers. See what I mean?

[spork]

I can only say that my experience has shown huge differences between ground/ground and ground/air transmissions. I have done range tests with antenna fully extended and been astounded at how limited they were. This is on flat ground with no objects blocking the LOS. This is easily tested by anyone that cares to try it.

The other case I mentioned was the case of 2 meter handhelds communicating hundreds of miles. Far far greater distances than I've ever known them to operate over ground.



2. As noted, even on that "reference" page, RF is Line of Sight. XPS claims that LOS does not apply to their TX module and RX. How can this be possible when all RF is LOS?

I don't think this explains their claim, but RF will also refract around "opaque" objects.

[Pinecone]

Maybe because they aren't using a totally stock Xbee module?